Refrigerating apparatus



Aug. 24, 1937.

S. H. COWIN REFRIGERATING APPARATUS Original Filed April 18, 1934 2 Sheets-Sheet 1 IN NTOR.

Aug. 24, 1937. I s H cowm Re. 20,477

REFRIGERATING APPARATUS Original Filed April 18, 1934 2 Sheets-Sheet 2 Reissued Aug. 24, 1937 REFRIGERATING APPARATUS Stuart B. Cowin, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a cor- 1 poration of Delaware p Original No. 2,053,945, dated September 8, 1936,

Serial No. 721,183, April 18, 1934. Application for reissue January'l, 1937; Serial No. 119,470

8 Claims.

This invention relates-to refrigeration and more particularly to the conditioning of air.

An object of this invention is to provide a method and apparatus for conditioning air in a 55 balance the constant volumetric capacity or heat dissipating power of the compressor unit with the varying refrigeration demands upon the system. When the refrigeration demands are relatively small, the compressor'unit tends to remanner to balance the varying heat absorption duce the refrigerant temperatures in the evap- 5 from the air withthe heat dissipation, from the orators to the point where moisture from the system, and to overcome: the tendency to ,proair freezes on the evaporators and eventually duce detrimentally low temperatures in the air clogs them. Also there is a tendency for the cooling devices or zones when the total refriger suction lines to become frosted because of unaation load is relatively small; or where one or lvoidable suction of liquid refrigerant from the 10 ,more of a plurality of air conditioning zones are evaporators. It is to the avoidance of these and inactive. other undesirable results that this invention is Further objects and advantages of the present directed. invention .will be apparent from the following Means are provided for compensating or haldescription, reference being had to the accomancing the constant volumetric or, heat dissi- .panying drawings, wherein a preferred form of pating capacity of the unit I 6 whileit is operthe present invention is clearly shownating with thewarying heat absorption or evap- In the drawings: oration in the evaporators I3, II and I5. To Fig. l isa diagrammatic representation of an this end, heat absorption or automatic pressure apparatus embodying features of my invention; limiting means in the form of valve 23 is placed 20 nd I in the suction passage I8 which automatically Fig. 2 is a cross-sectional'view of a type of limits the fall in pressure in the suction conpressure regulating valve which may be used in nection I8 adiacent the evaporators and prethe suction line. vents the refrigerant vapor pressure or tempere In practicing my invention, the air in oneor ature in the evaporators from falling suflicient- ,25

more comp t spaces H and is lylow to cause freezing of moisture'jrom the air conditionedby the cooling action of one or more on the evaporators. Also means are provided for v p t r r p r ng Z n 3; l4 and l5 controlling the flow of refrigerant to the variwhere heatabsorption from-the air, or refrigei'aous evaporators in accordance with the retion load, varies from time to time. The refrigeration demands of the air in the various 30 frigerflnt porated in these evaporators is conspaces. Thus. the flow of liquid refrigerant from veyed to refrigerant liquefying unit I6 where the line II to, the evaporators l3, I4 and I5 is the heat dissipation from the Sys tends controlled by means of automatic expansion mally to be constant. Here the refrigerant .15 valves 24, 25 and 26 each of which tends to feed liquefied and is returned through the liqu d liquid refrigerant into the evaporators when 35 frigerent e I1 150 the v p r The evapthe pressure therein falls belowa predetermined orated refrigerant is conveyed Q the plimit. The thermostatic bulbs 21, 28, and 23 are orators to the unit I6 through the suction line placed in the connections 30, 3| and 32 from or'connection I8. The re i llquefyihg 0 the outlets of the evaporators to thesuction line compr s r un l5 y include P l8. These thermostatic bulbsthrottle the valves 40 I9, a condenser 20, l q refrigerant. receive! 24, 25 and 2B whenever the liquid refrigerant in and motor 22 which drives the co p the evaporators tends to spill over" into the IQ. i suction line. In addition, thermostatic controls I M In an air. conditioning me od apparatus 01 in the form of thermostatic switches 33, 34 and this kind, not on y the to l refrigeration 108d 35 are placed near the air inlets to the air con- 45 from all of the evaporating Zones is likely to ditioners 36, 31 and 38 where the air is represenv y Widely from time to time, but h individual tative of the air in the compartments I I), II and .load on any evaporating s 8-150 quite I2 respectively. These thermostatic switches likely to vary Wide y The Volumetric e p control the flow of refrigerant inthe respective and hence heat dissipa g p we compressor evaporator-s and control the operation of the 50 I9, on the other hand tends to be constant 138- compressor through the motor 22, causing it to cause of the constant speedcharacteristics of stop when all of said switches are open and to the more desirable modern motors. Thus comstart when one or more of the switches are plications result unless means are provided to closed. 'This is accomplished by placing solenoid valves 39, 40 and 4| adjacent valves 24, 25 and 26. These solenoid valves prevent flow of liquid refrigerant into the respective evaporators when the temperature in the respective spaces Ill, ll and-i 2 falls below a predetermined limit, and 5 permit the flow of liquid refrigerant into the evaporators when that temperature rises above a predetermined limit. In addition, the switches 33, 34 and 35 control the operation of the compressor l9 and are therefore connected to the relay 42 so that the contact 43 is opened when all of the thermostatic switches are open and is closed when any one of the switches is closed. The relay 42 controls the starting and stopping or motor 22 and compressor I9.

In addition, motor driven blowers 44, 45 and 46, which cause the circulation of air over the evaporators are controlled by means of manual switches 41, 48 and 49, which switches are in series with the thermostatic switches 33, 34 and 35 so that any one air conditioner, and all its functions, may be cut in or out by closing or opening its respective manual switch.

The air conditioners 35, 31 and 38 may be of any type desired. In this particular embodiment, they may take the form of vertical casings having air inlets 50, 5| and 52 at the bottom, where the air flow is indicated by arrows, and having air outlets 53, 54 and 55 at the top above blowers 44, 45 and 46. The evaporators I3, I4 and I5 are placed within the casings as will be readily apparent from the drawings. Drain pans 56, 51, 53 are placed at the bottom of casing to catch any moisture condensed on the evaporator. Fig. 2 shows a type of valve which may be used in the suction line l8 and which is diagrammatically represented at 23 in Fig. 1. Refrigerant from the evaporators enter the check valve 23 at the inlet 60 and leave through the outlet 8| from whence they continue to the compressor. The valve structure 23 includes valve seats 52 and 63 upon which the balanced valves 64 and 55 seat. These valves are mounted on a stem 'GGupon which a bellows 61 is secured. The bellows 61 is also secured to the casting 68 so that the interior of the bellows is subjected to any constant pressure such as atmospheric pressure. The bellows is also provided with an adjustable spring 69 which may be adjusted by means of the screw 10 to calibrate the valve.

Passages H are provided so that the outside of the bellows is subjected to the evaporator pressure.. As the pressure is decreased the bellows is expanded and thus tends to throttle or close -.the valves. I

The stem 56 may be octagonal in cross-section with the sides 80- of the octagon tapering toward each end of the stem. This provides a relatively small bearing surface at the center of the stem to permit free play at both ends of the stem.

In operation, the refrigerant liquefying unit I6 is started whenever any one or more of the switches 33, 34 or 35 are closed by rise in temperature in that environment. If the refriger-.

ating load imposed on the one or more evapo- 5 rators happens to be the same as the heat dissipating capacity of the unit-16, the valve 23 opens fully and permits the compressor H to withdraw refrigerant from the active evaporator or evaporators to its'full capacity. However, if the re- 70 irigeratingv load imposed on.the active evaporators diminishes, due to low outside atmospheric temperatures, or because one or more of the evaporators are rendered automatically or manually inactive, the load is quite likely not to balance with the normal heat dissipating capacity of the unit It. Under these conditions, if it were not for action of valve 23, the unit It would reduce the vapor-pressure, and hence the temperature, of the liquid refrigerant in the active evaporators to the point where moisture from the air would be frozen on the surfaces of the evaporators. If this would occur, the refrigeration load would be further decreased by the reduced flow of air through the ice clogged passages and thus the undesirable. condition would be aggravated. With the valve 23, on the other hand, the flow of refrigerant to the compressor, and hence the heat dissipating capacity of the compressing unit It, is throttled or lim-' ited to the extent that it cannot reduce the vapor-pressure and temperature of the refrigerant in the evaporators to a point where moisture from the air would be frozen on them. Thus proper temperatures are maintained on the air cooling surfaces of the apparatus so that air may be properly cooled and moisture may even be condensed, but not frozen, on them regardless of the variance between the heat absorption by the evaporators and-the normal heat dissipating capacity of the compressor unit. An efilcient and satisfactory mode of conditioning air is thus provided.

While the form' of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that otherforms might be adopted, .all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An air conditioning apparatus comprising a compressor, a motor driving said compressor, a condenser connected to said compressor, a plurality of air conditioning evaporators connected to said condenser, a suction connection between said evaporators and said compressor, a device responsive to a psychrometric function of air controlling the evaporation of refrigerant in one of said evaporators, and means automatically limiting the quantity of refrigerant compressed by said compressor while operating to prevent said compressor from producing a vapor pressure in said evaporators sufliciently low to cause freezing of moisture on said evaporators.

2. An air conditioning apparatus comprising'a I compressor, a motor drivingsaid compressor, a condenser connected to said compressor, a blower for each evaporator, a plurality of air conditioning evaporators connected to said condenser, a

suction connection between said evaporators and said compressor, a device responsive to a psychrometric function of air controlling the evaporation of refrigerant in one of said evaporators, and means automatically limiting the quantity of refrigerant compressed by said compressor while operating to prevent said compressor fromproducing a vapor pressure in said evaporators sufliciently low to cause freezing of moisture on said evaporators. i

3. An air conditioning apparatus comprising a "compressor, a motor driving said compressor, a

condenser connected to said compressor, a plurality of air conditioning evaporators connected to said condenser, a suction connection between said evaporators and said compressor, aswitch responsive to a psychrometric function of air for each evaporator, each switch controlling the evaporation of refrigerant in the respective evaporator and said switches controlling said motor to cause said motor to stop when all of said switches are open and to start when one or more of said switches are closed, the means automatically eon-:7

limiting the, quantity of refrigerant compressed by said compressor while operating to prevent said compressor from producing a vapor pressure in said evaporators sufficiently low to cause freezing of moisture on said evaporators.

4. An air conditioning apparatus comprising a compressor, a motor driving said compressor, a condenser connected to said compressor, axplu rality ofair conditioning evaporators connected 7 to said condenser, a suction connection between said evaporators and said compressor, a switch responsive to a psychrometric function of air for each evaporator, each switch controlling the evaporation of refrigerant in the respective evaporator and said switches controlling said motor to cause said motor to stop when all of said switches are open and to start when one or more of said switches are closed and an automatic pressure limiting valve in said suction connection limiting the fall in pressure in said suc- .tion connection adjacent said evaporators below a refrigerant vapor pressure sufficiently low to cause freezing of moisture on said evaporators. 5. An air conditioning apparatus comprising a compressor, a motor driving said compressor, a condenser connected to said compressor, a plurality of air conditioning evaporators connected to said condenser, a suction connection between said evaporators'and said compressor, a device responsive to a psychrometric function of air 1 controlling the evaporation of refrigerant in one of said evaporators, and an automatic pressure limiting valve in said suction connection limiting the fall in pressure in said suction connection adjacent said evaporators below a. refrigerant vapor pressure sufficiently low to cause freezing of moisture on said evaporators.

6. The method of conditioning air in a plurality of air spaces which comprises compressing a refrigerant in a compressing zone as long as a psychrometric function of air in any one of said spaces is above a predetermined limit, condensing said refrigerant and conveying portions to evaporating zones into thermal exchange with the air in said spaces and thereby causing evap-" oration, withdrawing evaporated refrigerant from said evaporating zones and returning it to said compressing zone, controlling the flow of refrigerant in said evaporating zones in accordance with a psychrometric function of the air in said air spaces, and limiting the return of refrigerant to said compressing zone while compressing refrigerant to maintain the refrigerant temperature in said evaporating zones suiilciently high to prevent freezing of moisture from said air.

7. The method of conditioning air in a plurality of airspaces which comprises compressing a refrigerant in a compressing zone'as long as a psychrometric function of the air in any one ofv said spaces is above a predetermined limit, condensing said refrigerant, conveying portions of said condensed refrigerantfor evaporation in evaporating zones in thermal exchange with continuously circulated air in said spaces, controlling the conveyance of said portions in accordance with a psychrometric function of the air in said spaces; withdrawing evaporated refrigerant from said evaporating zones and returning it to said compressing zone, maintaining normal compressing capacity in said compressing zone such that said evaporating zones do not .freeze moisture from the air, and throttling the return of evaporated refrigerant to said compressing zone while compressing refrigerant when said evaporating zones evaporate an amount of refrigerant below the normal compressing capacity in said compressing zone to maintain the evaporating pressure in said evaporating zones sufficiently high to prevent freezing of moisture from the air.

8. The method of conditioning air in a plurality of air spaces which comprises compressing a refrigerant in a compressing zone as' long as a, psychrometric function of the air in anyone of said spaces is above a predetermined'limit, condensing said refrigerant, conveying portions of said condensed refrigerant for evaporation in evaporating zones in thermal exchangewith continuously circulated air in said spaces, controlling the conveyance of said portions in accordance with a psychrometric function of the air in said spaces, withdrawing evaporated refrigerant from said evaporating zones and returning it to said compressing zone, maintaining normal compressing capacity in said compressing zone such that said evaporating zones do not freeze moisture from the air, throttling the return of evaporated refrigerant to said compressing zone while compressing refrigerant when said evaporating zones evaporate an amount of refrigerant below the normal compressing capacity in said compressing zone to maintain the evaporating pressure in said evaporating zones sufliciently high to prevent 

